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Can we develop a solar heater based on coffee makers?
I was thinking the main problem in solar water heating - is that the solar panel is on the roof, and the storage tank is below it - Convection flow won't allow flow, so we have to pump it there - more energy.
However - coffee makers (filter type) heat the water at the bottom, and this produces gas pressure to lift the hot water up . It then repeats in small cycles of heating and moving water.
Obviously water won't boil in a solar heater to do this - but Dichloromethane will.
By fitting two or more non return valves in the system to ensure one way flow, and purging the system of all air. The Dichloromethane will do the work by itself. A pressurised expansion tank is all that is needed.
Dichloromethane boils at 40 degrees celcius - turning to vapour within the solar heater - expelling all the hot liquid. this returns to liquid when not heated in the pipes and water tank, creating a negative pressure. The non-return valves ensure the solar heater is filled again - assisted by the pressureised expansion tank, and a second heating cycle is started.
This will continue untill nightfall.
If the coil inside the water tank is at the bottom, then a further heating stage can take the water from 40 degrees to 60 - only a 20 degree raise. This may be by using another liquid of a higher boiling point.
What do you think?
Secondary heating can be by Methanol - boiling at 67 degrees celcius.
Complete automation !
Freezing points for these two are -95 and -97 degrees celcius - so no danger there - so can be left as a permanent fixture throught the winter. It may even produce heat on bright days.
However - coffee makers (filter type) heat the water at the bottom, and this produces gas pressure to lift the hot water up . It then repeats in small cycles of heating and moving water.
Obviously water won't boil in a solar heater to do this - but Dichloromethane will.
By fitting two or more non return valves in the system to ensure one way flow, and purging the system of all air. The Dichloromethane will do the work by itself. A pressurised expansion tank is all that is needed.
Dichloromethane boils at 40 degrees celcius - turning to vapour within the solar heater - expelling all the hot liquid. this returns to liquid when not heated in the pipes and water tank, creating a negative pressure. The non-return valves ensure the solar heater is filled again - assisted by the pressureised expansion tank, and a second heating cycle is started.
This will continue untill nightfall.
If the coil inside the water tank is at the bottom, then a further heating stage can take the water from 40 degrees to 60 - only a 20 degree raise. This may be by using another liquid of a higher boiling point.
What do you think?
Secondary heating can be by Methanol - boiling at 67 degrees celcius.
Complete automation !
Freezing points for these two are -95 and -97 degrees celcius - so no danger there - so can be left as a permanent fixture throught the winter. It may even produce heat on bright days.
1 Answers
The idea of using convection to move water in a solar water heater is the basis of "thermosiphon" water heaters. They actually do place the tank at a higher level than the panels. However, it seems that it takes so little energy to run a pump, that using a pump is the most popular way to move the water, and the heat.
In areas where it will get cold, you have to worry about freezing. Hopefully your Dichloromethane wouldn't have that issue. A common system uses Propylene Glycol (antifreeze) to carry the heat from the roof to the tank.
By the way, a nonconcentrated solar thermal panel *can* boil water. If the box is well insulated, the water exceeds 100 C. Check out the book, "From Space to Earth - The Story of Solar Electricity" at your library.
In areas where it will get cold, you have to worry about freezing. Hopefully your Dichloromethane wouldn't have that issue. A common system uses Propylene Glycol (antifreeze) to carry the heat from the roof to the tank.
By the way, a nonconcentrated solar thermal panel *can* boil water. If the box is well insulated, the water exceeds 100 C. Check out the book, "From Space to Earth - The Story of Solar Electricity" at your library.
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